Screws, anchors, and joints: the weak points of any metal structure

If you check any metal structure that is a few years old, you will see that rust almost never starts in the middle of a beam. It starts on the screws, the nuts, the anchor plates, the welds, and the edges. These are the weak points, and they are where you need to pay the most attention.

Why joints rust first

• They collect water and dirt: the gaps between parts retain moisture for hours.
• They are assembled after galvanizing: field screws, cuts, and holes drilled during assembly are left unprotected.
• The paint is thinner on edges: on a sharp edge, the paint recedes and leaves a thinner layer.
• Welds burn off the zinc and leave the surrounding steel exposed.
• Galvanic pairs: bringing different metals together (for example, untreated fasteners on galvanized steel) accelerates corrosion.

How to protect them properly

1. Clean thoroughly with a steel wire brush: you need to reach solid metal even in the recesses.
2. Degrease with xylene; screws usually come with factory oil.
3. Brush coat first: before the general coat, apply GALVANOL with a brush to welds, screws, edges, and corners. This is what its technical data sheet recommends for difficult areas.
4. General coat on the entire part.
5. Repeat the general coat; at critical points, don't worry if it leaves a slightly thicker layer (without exceeding 200 µm).

Spray for already assembled fasteners

For post-assembly screws, anchor bolts, and touch-ups on site, GALVANOL Spray 500 ml is the fastest way: it reaches corners where a brush struggles and leaves a uniform layer. Shake it well, apply it from 25–35 cm away, and give it two or three thin coats.

Compliance with standards

GALVANOL complies with ISO 1461 and ASTM A780 as a hot-dip galvanized repair coating, so it is suitable for repairing cuts, holes, welds, and assembly screws on galvanized structures. If you want to know more about how to do it, read our guide on repairing welds and cuts in galvanized steel.